I would like to replace an Hbridge circuit that has 2 SPDT relays with MOSFETs.
The design parameters are as follows:
VBUS - 13VDC nom (12min 14max)
Icont - 50A
IPeak - 75A (intermittent still 3 mins so basically its still cont)
75A max On 5mins Off 3 mins
The circuit is controlled by manual operation that will operate a brushed DC motor FWD and REV. There is no uC and no PWM.
I have been looking at various MOSFET datasheets and have not been able to find any that would allow me to run VBUS into the Gate and have VDS just pass the current through.
I was looking at the Safe Forward Operating Area graphs and it seems like with almost any of the MOSFETs that a VDS of ~12VDC puts me extremely low on the available current allowed on avg ~10A.
For example http://www.vishay.com/docs/71903/sum85n03.pdf
On the safe operating area of the graph for a VDS of ~12VDC the ID would be ~8A if I am reading it correctly. Since there is no Micro I need to use DC values.
I can Change Vgs with a Voltage Divider but I cant change VDS. The only thing I can think of is to use parallel MOSFETs.
Any suggestions would be of help.